Mass transfer columns, such as distillation, absorption, and stripping columns, have been provided with various types of contact trays for vapor-liquid contact purposes. These columns are well known in the art for separation of a multi-component feed stream(s) and are not particularly limited herein. Examples of such columns and trays are described in U.S. Pat. Nos. 4,750,975; 5,120,474; 5,453,222; and 8,066,264, which are incorporated herein by reference.
Typically, a mass transfer column has a plurality of contact trays horizontally disposed in a spaced apart configuration over the height of the column. A typical contact tray has a deck over which a flow of liquid passes from an inlet downcomer section to an outlet downcomer. The typical tray deck has orifices through which an ascending vapor may flow and over which the liquid may flow in order to bubble or otherwise force the vapor through the liquid in cross-current flow.
A tray is designed to contact liquid and vapor and then allow their separation. In its simplest conceptual form, vapor flows up through holes in the tray deck and contacts liquid. The two disengage and liquid flows downward through the downcomer to the tray below and vapor flows up to the tray above. Since the vapor-liquid contact is intimate, there are mixtures of vapor and liquid almost everywhere on the tray. When operating under certain conditions, such as elevated pressure, mixing of liquid and vapor can result in the presence of froth (e.g. a mixture vapor and liquid) on the tray deck(s). Froth can buildup and flow into the downcomer carrying entrained vapor down through the downcomer and/or can flow upward through the holes of the tray above carrying entrained liquid. The efficiency and capacity of the tray and hence the column can be reduced by the occurrence of either event.
Design of distillation columns and their associated internals is a balance of overall material throughput and tray/column efficiency. Accordingly, it is an object of the invention to improve the capacity and efficiency of a tray for a mass exchange column.